This procedure only needs to be performed upon initial use of the analyzer or in the transition from buffer adjustment with a pH meter. It should be repeated 1) if there is a change to the deionized water system, 2) when a new batch of Buffer Adjustment Solution is prepared, or 3) if the background offset no longer falls between 20000 and 40000 on Gain 1000.
Timberline no longer recommends adjusting the background of the buffer using a pH meter. Adding a known quantity of the ammonium hydroxide solution based on the Offset DAQ setting on the analyzer is preferred. This simplifies the buffer preparation and eliminates potential contamination from a pH meter.
All of the following Steps should be done with a Gain setting of 1000. Once the buffer check is completed, the gain should be set to the appropriate setting for the calibration range. Note that the offset will change with the gain setting.
Contaminated glassware may increase the background offset. Timberline recommends using dedicated reagent bottles.